Method and arrangement for channel type switching

ABSTRACT

The present invention relates to a method for improved and efficient usage of radio network resources with regard to the transmission properties of applied communication channel types and total network load by means of using early indications on the uplink or downlink of requests to establish new communication connection or adjust parameter settings of already existing connections regading the expectable amount of additional traffic due to such a connection. Early indications are, e.g., information on protocol type, the kind of requested communication service, the profile of the user equipment that has sent the request, or traffic history. In response to such indications the inventive method can forward, e.g., an uplink request and at the same time initiate a channel type switching providing appropriate channel parameter settings or adjustments. In case of congestion control it is another possibility to delay or even suppress uplink requests.

FIELD OF THE INVENTION

The present invention relates to a method for improved and efficientusage of radio network resources with regard to the transmissionproperties of applied communication channel types and the total networkload.

BACKGROUND OF THE INVENTION

Modern radio communication systems are developed to be able to supportvarious kinds of network services to end users. Apart from ordinaryspeech connections such services can relate to, e.g., the transfer ofvideo data or the download of portions of packet data. Apparently, thisrequires a radio communication network that is prepared to handlecommunication connections for carrying traffic with considerablydifferent characteristics. Said traffic can be distinguished, e.g. bymeans of the required transmission properties, e.g. bandwidth, delays,or bit error rates; the main traffic direction, i.e. bidirectional ormainly asymmetric; or the traffic density, i.e. whether the traffic flowis more or less constant or occurs in bursts. Four types of trafficclasses have been defined for the UTRAN environment with respect torequirements on, e.g., delay, delay variations, or packet loss: Thetraffic class “conversational” requires typically short delays, aminimum of delay variation, and in-sequence delivery but a moderatepacket loss. Examples of applications are bi-directionalperson-to-person communication such as voice or video telephony andgames. Another traffic class, “streaming”, requires moderate delays, aminimum of delay variations, in-sequence delivery but low to moderatepacket loss. Examples of applications are unidirectional communicationto humans, e.g. real-time audio and video streaming. A third trafficclass “interactive” denotes typically information transfer from a serverto a human or computer, e.g. Internet-related exchange of information,and requires reasonable low delay and low packet loss. Finally, a fourthtraffic class denotes “background” traffic that relates to, e.g., thetransfer of e-mail, files, or short messages and requires low packetloss but used for services that can accept longer delay and high delayvariations.

In third generation cellular mobile communication systems, e.g.WCDMA-based communication systems, a number of radio channels withdifferent characteristics have been defined in order to be able tohandle traffic that is characterised by such various requirements:

A common channel is common to a number of user equipments, typically toall or a part of the user equipments in a cell. When using these typesof channels, each data block that is sent on the channel needs tocontain some kind of identity of the source and destination userequipment. Due to their limited capacity these channels are preferablyused for the transmission of small portions of packet data. Anothercharacteristic of the common channel is that the power on the uplink iscontrolled in a slow way and fixed for the downlink common channels.Examples of common channels in WCDMA for the uplink are the PhysicalRandom Access Channel (PRACH) and the Physical Common Packet Channel(PCPCH). An example of a common channel on the downlink for aWCDMA-system is the Secondary Common Control Physical Channel (SCCPCH).

A dedicated channel is assigned exclusively to one user equipment andmay be used by only this user equipment. This channel provides fastpower control and soft handover. Dedicated channels are associated witha maximum bit rate, which is assigned when the channel is established.The transmitter may then use different sizes of transmitted blocks up toan allowed maximum value in order to accomplish a variable bit-ratechannel but the assigned codes can not be used by other users when thereis less to transmit than the maximum rate. An example of a dedicatedchannel in a WCDMA-system is the Dedicated Physical Channel (DPCH),which is a bi-directional channel.

A shared channel is shared by a set of user equipments in a cell.However, instead of identifying each transmitted block with the mobileidentity, as done for common channels, the information on which blocksare used by which user equipment is provided separately, i.e. such asdone on an associated DPCH to each user equipment. A scheduling functiondecides for which user equipment the data is sent. These channelsprovide a variable bitrate for each user but still uses the codesefficiently. Examples of shared channels in WCDMA-systems are thePhysical Downlink Shared Channel (PDSCH) and the Physical Uplink SharedChannel (PUSCH).

Each type of channel provides a unique set of characteristics and,regarding the fact that a variety of services must be provided to theuser equipments, it becomes obvious that there is not one single channeltype that is optimal at every point in time and for each type ofservice. Therefore, it is necessary that there are control functions toselect which channel type or types should be used by each user equipmentat each point in time.

In WCDMA-systems, a prior known solution for this requirement is theintroduction of a function for traffic volume measurement that isimplemented in the Radio Network Controller (RNC) as well as in theMedium Access Control (MAC) sublayer of the user equipment. The MACperforms a scheduling of data transmission on the radio channel. Forthese reasons, the MAC continuously polls the data buffers in the RadioLink Control (RLC) sublayer for any data to transmit. When there is datain the buffers, the MAC takes data from the RLC-buffers and schedulesthe transmission of the data on the radio channel. The traffic volumemeasurement function in the MAC checks the amount of data in theRLC-buffers. When the total amount of data in the RLC-buffers, e.g.,exceeds a limit controlled by the network, a measurement report message,which includes inter alia information about the amount of data in thebuffers, is sent to the network. The network on the other hand monitorsthe traffic volume in a similar way, but the measurement report messageis generated internally in the Radio Network Controller. The resultsfrom the traffic volume measurement function in the RNC and the receivedmeasurement reports from the mobile station are fed into a “channel typeswitching function” in the RNC. This function may order the connectionto a mobile station to switch from a certain combination of channeltypes, e.g. the PRACH and the SCCPCH, to another combination, e.g. theDPCH.

WO 99/66748 discloses a method and apparatus for dynamically adapting aconnection state in a mobile communication system. A packet dataconnection between a mobile station and a radio access network isestablished where the state of the connection is used to specify one ofplural different types of radio channels. The connection is dynamicallyadapted to an optimal state based on one or more conditions relating tothe connection.

FIG. 1 a shows an overview of a layered protocol structure of units in acommunication system as presented in FIG. 1 b. The description ofmethods for channel switching according to the state of the art andaccording the present invention will rely upon these figures. Thiscommunication system consists of a mobile radio communication system 10and a packet-switched network 20, e.g. the Internet. The radiocommunication system 10 is intended to provide services to a pluralityof user equipments 11 that roam within its coverage area. Said userequipments 11 are connected to one or more radio base station 12, whichare controlled by Radio Network Controllers (RNC) 13. The Radio NetworkController 13 is responsible for a variety of tasks related to thehandling of communication traffic and system maintenance and providesalso connections 14 to other networks, e.g. a packet-based network 20that consists of a plurality of interconnected units 21,22 such thatuser equipments 11 in the radio communication network 10 can retrieveinformation from a remote unit 22 in said packet data network 20. Theuser equipment 11 performs an application protocol 117 on top of alayered protocol structure that uses, e.g., TCP (Transmission ControlProtocol) 116 or another appropriate protocol on top of IP (InternetProtocol) 115. These protocols rely in turn on, e.g., PDCP (Packet DataConvergence Protocol) 114, which performs a compression of theTCP/IP-headers to reduce the packet sizes sent over the radio interface,RLC (Radio Link Control) 113, and MAC (Medium Access Control) 112.Finally, the physical layer 111 is responsible for the physical dataexchange on the radio channel. The RNC 13 provides a correspondingprotocol stack in order to be able to handle the forwarding ofIP-packets. The RNC 13 is also capable to perform the necessaryprotocols on the physical layer (L1) 131 and the link layer (L2) 132 forhandling IP-packets in the packet data network 20. Finally, apart fromthe appropriate layer 1 and layer 2 protocols and IP 223 the remote unit22 in the packet data network to which the user equipment 11 intends toestablish a connection must be equipped with TCP 226 and the applicationprotocol 227 that corresponds to the application protocol 117 in theuser equipment.

FIG. 2 a shows a time flow diagram for the establishment of a connectionaccording to the state of the art that shall be applied for informationdownload, e.g. web browsing, from a remote unit in a packet data networkto a user equipment in a radio access network. The application uses HTTP(Hypertext Transfer Protocol) to fetch webpages, which layout isdescribed in HTML (Hypertext Markup Language), from a web server. HTTPin turn uses TCP on top of IP for data transmission. For each HTML-page,or sometimes even for each object on the HTML-page, a TCP-connection isestablished and then the bursts of data are transmitted from the webserver to the web browser in the user equipment. This data exchange canbe subdivided into three phases: In the first phase, a TCP-connection isestablished by means of sending a TCP-segment comprising a SYN-flag inits header field from the user equipment to the web server through theradio communication system and the packet data network. The web serverthen acknowledges the establishment of the TCP-connection by means ofsending a TCP-segment comprising an ACK-flag it its header field back tothe user equipment whereupon also the user equipment acknowledges bymeans of sending a TCP-segment comprising an ACK-flag. Thisestablishment of a connection implies a delay time τ1. Then, in a nextphase the content of the HTML-page is sent in TCP-segments from the webserver. On its way to the user equipment they pass the mobile systemwhere they are buffered and wait to be scheduled for transmission overthe radio interface by the MAC. At a point T1 in time when the trafficvolume measurement function detects that the amount of data in theRLC-buffers in the mobile system exceed a certain threshold value, itinforms the “channel type switching function”, which triggers a changeof the channel type. At a point T2 in time after a delay period τ3thechannel switching is completed. There is thus a certain delay _(τ2)between the point T0 in time when the information download to the userequipment is started and the point T2 in time when an appropriatechannel type is available for said information download. During saiddelay period τ2 the user will experience a slow response from theexternal server and a low data throughput.

SUMMARY OF THE INVENTION

A shortcoming of the prior-art solution as presented above results fromthe fact that the channel type selection and the channel parametersettings are triggered by traffic volume measurement reports. This leadson the one hand to comparatively long delays to establish a new type ofchannel when bursts of data need to be transmitted and, on the otherhand, to take measures in case of a reported upcoming network congestionsituation. These long delays result in low throughputs in terms of thetransmitted data rate, e.g. due to an inappropriate channel type ornetwork congestion, and are experienced by the end user as a slowresponse.

Therefore, it is an object of the present invention to achieve a methodthat provides an efficient usage of the radio network resources withregard to the transmission properties of the applied communicationchannel types and the total network load.

It is thus an object of the present invention to achieve a method forchannel type switching in radio communication networks that provides inan early stage an efficient and fast downlink connection.

It is thus another object of the present invention to achieve a methodthat initiates in an early stage measures to prevent a reported upcomingnetwork congestion.

Briefly, the method according to the present invention accomplishesthese objects by means of using early indications of requests toestablish a new communication connection or adjust parameter settings ofan already existing connection that are sent on the uplink or downlinkregarding the expectable amount of additional traffic due to such aconnection. Such early indications can be retrieved from information onprotocol type or protocol contents, the kind of requested communicationservice, the profile of the user equipment that has sent the request, ortraffic history. In response to such indications the inventive methodcan forward, e.g., an uplink request and at the same time initiate achannel type switching providing appropriate channel parameter settingsor adjustments. In case of congestion control measures it is yet anotherpossibility to delay or even suppress the uplink request. By this means,the method according to the present invention rather prevents thanreacts on an inefficient usage of channel or network resources.

It is a first advantage of the present invention that there is a shorterlatency before data can be transmitted at a higher average throughput,which results in shorter response and download times.

It is another advantage of the present invention that a lesser number ofRLC-buffers is needed because data is sent faster, which also implies alower memory demand in the user equipment.

It is still another advantage of the present invention that a lessernumber of measurement reports need to be sent from the mobile stationsince the channel type switching is triggered earlier, thus resulting inless signalling traffic.

Yet another advantage of the present invention is that it implies asimple solution with a minimum of complexity and with minimal impact onthe system architecture.

Other objects, advantages and novel features of the invention willbecome apparent from the following detailed description of the inventionwhen considered in conjunction with the accompanying drawings andclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding, reference is made to the following drawingsand preferred embodiments of the invention.

FIG. 1 a shows an overview of a layered protocol structure of units in acommunication system as presented in FIG. 1 b.

FIG. 1 b shows a communication system consisting of a radiocommunication system and a packet data network.

FIG. 2 a shows a time flow diagram for the establishment of anappropriate connection for information download from a remote unit in apacket data network to a user equipment in a radio access network whenusing the method according to the state of the art.

FIG. 2 b shows a time flow diagram for the establishment of anappropriate connection for information download from a remote unit in apacket data network to a user equipment in a radio access network whenusing the method according to the present invention.

FIG. 3 a shows a flowchart that illustrates an overview of the methodsteps of the present invention.

FIG. 3 b shows a flowchart that illustrates the method steps foradapting to possible traffic restrictions according to an alternativeembodiment of the present invention.

FIG. 3 c shows a flowchart that illustrates the method steps forperforming the channel type switching according to the presentinvention.

FIG. 4 shows an arrangement that is incorporated in or connected to aRadio Network Controller in order to perform the method according to thepresent invention.

DETAILED DESCRIPTION

The method according to the present invention is performed, e.g., in orat the site of the Radio Network Controller (RNC) 13 in a WCDMA-system10. It is one principal idea of the inventive method to predictexpectable downlink traffic in the radio communication network 10 asearly as possible by help of early indications that are sent via theRadio Network Controller 13 on the uplink, e.g. regarding the protocoltype or protocol contents and the kind of requested service for a newdownlink communication connection, the user profile, or traffic history.By this means a channel switching to an appropriate downlink channel canbe performed as early as possible, i.e. in parallel to the establishmentof the downlink communication connection between a remote unit 22 andthe user equipment 11. Similarly, said method can also be used to free adedicated downlink channel as soon as possible by using earlyindications for a connection termination which are received on theuplink or downlink. Early indications on the uplink or downlink can alsobe used for a congestion control in the radio communication network 10by means of reducing or delaying the traffic amount that is sent on theuplink or downlink. This reduction can be achieved either by suppressingor delaying, e.g., an uplink request, which prevents, at leasttemporarily, the generation of additional downlink traffic, or byreducing the assigned downlink bitrates.

The flowcharts of FIGS. 3 a-3 c will present the method according to thepresent invention, which is applied for a channel type switching inorder to reduce delay times on downlink communication connections. WhileFIG. 3 a presents the method steps in an overview flowchart, FIG. 3 bshows in particular the method steps for adapting to reported trafficrestrictions according to an alternative embodiment of the presentinvention and FIG. 3 c shows the method steps for performing the channeltype switching.

FIG. 3 a describes the overall method steps that are performed toachieve a faster switching to an appropriate downlink channel asperformed by a functional unit, e.g., incorporated in the Radio NetworkController: The method checks for indications of data packets that aresent on the uplink, e.g. from a user equipment in the radiocommunication network, to the RNC, or sent on the downlink to said userequipment, block 31. These indications can be retrieved from, e.g., thePacket Data Convergence Protocol (PDCP) that reads all throughpassingdata packets for performing a compression of header fields in order toreduce the packet sizes that must be sent over the radio interface.However, within the scope of the present invention it is likewisepossible to retrieve this information by other means. Said indicationsrelate inter alia to the protocol type, e.g. TCP or HTTP, but also topossible flags that indicate, e.g. a request for establishing acommunication connection for carrying a certain type of traffic or anindication to terminate a connection. Generally, the method according tothe present invention allows to use the content of received datapackets, e.g. the header field, sent in either uplink or downlinkdirection in order to make predictions of the expectable traffic on theuplink or downlink. If an indication of a recognised data packet typehas been received on the uplink, block 31 Yes, it is investigatedwhether this header field belongs to a data packet sequence or segmentthat contains an indication to terminate a connection, block 32 Yes, orcontains other kind of traffic indication, block 32 No, e.g., anindication on the uplink to establish a new downlink communicationconnection. Examples of detectable flags that indicate the establishmentof a new downlink communication connection are, e.g., a TCP SYN-commandfor establishment of a new TCP-connection, a HTTP GET-command, or a RSVPReserve command. For these cases the method according to the presentinvention can provide for at least one of the following measures: In afirst step, block 33, an admission control part can check whether anytraffic restrictions have been reported from the network, e.g. due to anear congestion state in the network, and determine in which way suchpossible restrictions should have an influence on the establishment ofan additional downlink connection as requested by the detected uplinkcommand. This will be explained in greater detail in FIG. 3 b. Inanother step, block 34, the method step will initiate the necessarysteps for performing a downlink channel type switching. This will beexplained in greater detail in FIG. 3 c. Thus, a channel type switchingand/or measures for a possibly necessary downlink traffic reduction aretriggered directly by the detection of, e.g., a protocol flag or acomparable indication on the uplink preceding to a new downlinkconnection. It is important to stress that these measures are initiatedbefore the corresponding downlink connection has been established, i.e.in parallel to said connection establishment. Apparently, the inventivemethod offers the advantages to establish a downlink connection forwhich the initial data transfer is experienced to be faster comparedwith the state-of-the-art solution while at the same time alsoconsidering the total network load. The merits of the invention willmainly depend on the fact how well the presumptions that lead to achannel switching correspond to the actual data transfer. After theestablishment of a new channel type or the introduction of trafficrestrictions traffic volume measurements can be initiated, block 35,that result in reports that may trigger further channel switchingsand/or adjustments of the channel parameters.

A similar problem as to initiate a channel switching as fast as possiblein the beginning phase of the establishment of a new communicationconnection is to release a connection as fast as possible after that ithas been terminated in order to free radio resources that are no longerused for other tasks. Therefore, if an indication to terminate adownlink connection is received on the uplink, block 32 Yes, the part ofthe downlink connection in the radio communication network can alreadybe freed at that point, block 36, instead of waiting until the externalremote unit from which information has been retrieved has terminated thedownlink connection. Still another conceivable alternative, which is notshown in the figure, could be to check the downlink connections forindications to terminate such a connection.

The efficiency of the method according to the present invention dependsto a conceivable degree on the quality of the decision to switch to acertain type of channel comprising certain channel parameter settingswith regard to the expected traffic and, in case of reported trafficrestrictions, to take the appropriate measures to prevent that a newestablished downlink connection makes a near network congestionsituation even worse. The selection of an appropriate channel type andthe channel parameter settings, e.g. the maximum bitrate, are a-prioridecisions that are taken before any data has been sent. Therefore, inorder to prepare appropriate measures to meet required trafficrestrictions, block 33, or in order to select the appropriate channeltype, block 34, for a new downlink connection, the method according tothe present invention will in both cases investigate available trafficindications on the uplink regarding said downlink connection, block 332,block 341.

The following paragraph will therefore discuss a selection of possibleindications that can be applied for these purposes by the methodaccording to the present invention: Two major indications for anestimation of the expectable additional traffic on the uplink ordownlink are the applied protocol type and the traffic class. Theprotocol type, e.g. TCP or HTTP, can provide indications, e.g., of theamount of traffic, the distribution in time or the main direction of thetraffic flow. The method according to the present invention can beadvantageously used for so called “interactive” or “background” traffic,which can be characterised as bursty and often asymmetric traffic. Thisimplies that comparatively huge portions of traffic are sent in onedirection at certain time periods while there is virtually no trafficduring the intermediate time periods and only little traffic in theother direction. The indication of the traffic class has also aninfluence with regard to the available resources that, e.g., the networkoperator has reserved for traffic of the respective traffic class. Inorder to make more exact predictions of the expectable amount of trafficand allocate an appropriate channel type it might also be possible toapply, e.g., a TCP-proxy. Another indication can be retrieved from thesubscription type of the user equipment that has sent the uplinkindication or to which a downlink indication is sent. Depending on thefact whether the subscription type guarantees, e.g., a prime typeservice or only a best-effort service it is possible to determine thechannel type selection and parameter settings and, if necessary, theseverity of possible traffic restrictions. It is thus possible to favourcertain user equipments regarding the accessibility to the network orthe assigned channel bitrate. The selection of the maximum bit rate fora new channel can also be based on parameters that have been used whenthe radio access bearer between user equipment and core network wasestablished. In addition to this, yet another conceivable indication canbe retrieved from traffic statistics that is collected in a networkunit, e.g. the Radio Network Controller. From this statisticsinformation can be retrieved on the communication that is transmitted toa user equipment or retrieved from a remote unit, e.g., on the amount oftransmitted data to a certain user equipment, the traffic behaviour ofthis data, e.g. bursty or asymmetric traffic, and the period of time forwhich a communication connection normally is used. Apparently, trafficindications within the scope of the present invention include aspects oftraffic conditions, e.g. related to the applied protocol type and thekind or amount of data traffic, aspects related to network conditions ornetwork operator preferences, e.g. the assigned resource shares for thevarious traffic classes, and finally aspects that relate to the userequipment that has requested for a communication connection, e.g. theuser subscription type.

FIG. 3 b shows the method steps to prepare appropriate admission controlmeasures to meet possibly required traffic restrictions, block 33: Bythis means the inventive method can be used in order to achieve animproved congestion control in the radio communication network. In anair-interface congestion situation, e.g. due to a lack of downlinktransmission power, the radio resource management function may be forcedto reduce temporarily the bitrates for connections to some userequipments. This has an influence on the ongoing data flows and maycause an excessive buffering in the network, which leads to high delaysand packet drops. If any traffic restrictions have been indicated, e.g.,by the network, block 331 Yes, it is at first necessary to investigatethe available traffic indications that have been received on the uplinkor downlink, block 332, as explained in the paragraph above. From thisretrieved information it must be decided whether traffic restrictionscan be taken into account for the requested downlink connection, block333, and which restrictions are applicable, block 334. These decisionscan be defined in accordance with the strategy of the network operator,e.g., to guarantee a fast and reliable service to as many userequipments as possible in the network. If the radio network is in a nearcongestion state and thus reports a need for traffic restrictions theinventive method can be used to restrict or even suppress additionaldownlink traffic. The network operator may decide to introduce trafficrestrictions for certain types of traffic, e.g. all traffic that is notreal-time sensitive, or for certain user subscription types, e.g. abest-effort subscription type. If such or other restrictions appear tobe applicable for the downlink connection that is to be established,block 333 Yes, it is up to the network operator to select an appropriatemeasure to put this restriction into practise, block 334. There areseveral possibilities to meet the requirement of a downlink trafficrestriction: The most severe alternative is to suppress the uplinkindication and by this means simply avoid any downlink traffic thatwould occur if the downlink connection is established, block 336. Thisalternative could be applied, e.g., for user equipments that have a lowprioritised subscription type. A more modest alternative is to delay theuplink indication for a shorter time period, block 337, which could beapplicable if the network reports shorter and temporary congestion peaksor if the network load is close but still below a certain congestionthreshold level. Still another alternative is to modify the downlinkchannel parameters depending on the expected traffic or protocol type.This could imply that the downlink bitrate is maintained, e.g., forreal-time sensitive traffic but selectively reduced, block 335, forother kinds of traffic. Apparently, the measures as described above arenot only applicable to meet requests for traffic restrictions but canalso be used by a network operator to favour, e.g., certain types ofusers or certain types of traffic.

Regarding the selection of a channel type, the establishment of acommunication channel is normally initiated via a common channel, whichis common to all user equipments in a cell or a part of a cell. However,as these channels have a limited capacity and slow power control theyare badly suitable for transmission of larger data portions. Therefore,it is desirable to use a dedicated channel or a shared channel for thetransmission of larger portions of data. Dedicated channels areexclusively assigned to a certain user equipment; however, there is onlya limited number of such channels, which probably are not efficientlyused in case of bursty and/or asymmetric traffic, which arecharacteristics of interactive or background traffic that the presentinvention focuses on. Shared channels can be used by several userequipments in a cell and comprise a variable bit rate for each user.These channels are well suitable for, e.g., interactive or backgroundtraffic. After the establishment of the new channel type, trafficmeasurement reports may be used to trigger a further channel typeswitching or to initiate adjustments of the maximum data rate. If, forinstance, the maximum rate has been selected too low, the rate at whichdata can be transmitted is lower than the rate at which data is receivedfrom the upper layer. This can cause that the data buffers will exceed adefined threshold level and thus trigger a traffic volume measurementreport. In this case it may be necessary to switch to a higher ratechannel or a different channel type. On the other hand, if the maximumrate has been set unnecessarily high, the RLC-buffers are emptied and atraffic volume measurement function may report that there is no data totransmit. In this case, it may be necessary to switch to a lower ratechannel or a different channel type.

FIG. 3 c show the method steps to perform a channel type switching. Asalready described above it is necessary to investigate the availabletraffic indications that have been received on the uplink or downlink,block 341. From this information an appropriate channel type can beselected, block 342. The channel parameter setting including possiblerestrictions, block 343, depends on said traffic indications. Themaximum channel bitrate or other parameters for the downlink channelthat shall be established can be determined from traffic relatedaspects, e.g. the expectable amount of additional downlink traffic orthe protocol type; from user related aspects, e.g. the user subscriptiontype; or from network related aspects, e.g. the network resources thathave been reserved for and are available for certain types of traffic orcertain types of users. Said maximum bitrate can also be determined fromthe parameters used when the radio access bearer was established.Finally, the channel type switching and parameter setting is initiatedon basis of the conclusions from these and other reported trafficindications, block 344.

FIG. 2 b describes in analogy to FIG. 2 a a time flow diagram for theestablishment of a connection that shall be applied for informationdownload from a remote unit 22 in a packet data network 20 to a userequipment 11 in a radio access network 10. The time flow in this figurehas been improved by help of the method according to the presentinvention. The comparison of FIGS. 2 a and 2 b will illustrate themerits of the invention regarding reduced response delays due to thefaster establishment of an appropriate communication channel.

A user equipment (UE) in a radio access network that intends, e.g., toretrieve data from a remote unit in an external network by means of aTCP/IP-connection will send a TCP-header containing a SYN-flag to saidremote unit via the RNC that controls the network part within which saiduser equipment is located. The remote unit will acknowledge theconnection request by means of responding with a TCP-header containingan ACK-flag. This connection establishment will cause a certain delay_(τ1) before any data actually is transmitted from the remote unit. Itis now the idea of the present invention to initiate a switch to anappropriate channel type comprising an appropriate setting oftransmission parameters already during the establishing phase, i.e. at apoint in time T₁ when the RNC, e.g. via the PDCP, has received anindication on the uplink of the protocol and the type of traffic forwhich a downlink connection shall be established to a user equipment.The channel type switching implies a certain delay _(τ3) after which thenew channel can be applied. An apparent merit of the invention is thatthe time period _(τ2) during which data is transmitted via a non-optimalchannel is considerably shorter compared to the solution according tothe state of the art.

In FIG. 2 b the merits of the method according to the present inventionare demonstrated by help of the example of user equipments that retrieveuser-related data. Said data transfer is experienced to be faster in theinitial phase. However, the inventive method can also be successfullyapplied for data retrieval that is not visible for the end user. Thiscould typically be any kind of background traffic that is transmitted atirregular times and necessary for exchange of various control andsignalling information. Another example is the download of software tothe user equipment. This traffic is necessary on the one hand butimplies on the other hand a decrease of the network capacity for usertraffic. Therefore, it is advantageous to apply the method according tothe present invention in order to be able to perform the data transferfaster and to free downlink channel that are used for such traffic assoon as possible when the data transmission has been completed.

FIG. 4 shows an arrangement 40 that is incorporated in or connected to aRadio Network Controller 13 in a radio communication system 10 in orderto perform the method according to the present invention. Saidarrangement 40 comprises means 41 for retrieving information of datapackets that are sent on the uplink from said user equipments to one ofthe Radio Network Controllers. This information is checked by a unit 42for a correspondence to one of a selection of known packet header typesthat is stored in a record field 44. The arrangement comprises means 43for investigating recognised data packet headers containing a request toestablish a communication connection. If a request to establish aconnection has been detected the arrangement 40 can apply means 46 forperforming a channel type switching to an appropriate channel typecomprising appropriate channel parameter settings on basis of thetraffic indications that have been received on the uplink in parallel tothe further establishment of the communication connection. An optionalunit 45 can be used to check for possible traffic restrictions that arereported, e.g., from the network. In this case, said unit 45 caninitiate possible restriction measures for the communication connectionto be established before a channel type switching is performed in unit46. As already explained above, said restriction measures rely ontraffic indications, e.g. related to the protocol type, that have beenreceived on the uplink. Possible restriction measures are, e.g., tosuppress or delay a received uplink data packet header containing arequest to establish a new downlink communication connection or toreduce the bitrate for this new downlink communication connection. Thearrangement 40 also comprises means 47 for investigating recognised datapacket headers containing a request to terminate a communicationconnection. In case of a request to terminate a connection thearrangement 40 can apply a unit 48 that terminates the radio connectionpart of said existing communication connection.

Hitherto, the method and arrangement according to the present inventionhave been described with focus on a WCDMA-based radio communicationsystem using a Radio Network Controller 13. However, it isnotwithstanding possible to apply said invention also in other kinds ofradio communication systems. The inventive method could also be appliedtogether with other node types that are responsible for traffic control,e.g. between user equipments in said radio communication system andother remote units, and have an influence on the channel settings forcommunication connections between said units. Examples of such nodes area Base Station Controller (BSC), a Packet Control Unit (PCU), or aMobile Services Switching Centre (MSC). Still other examples ofconceivable nodes are a Serving GPRS Support Node (SGSN) or a GatewayGPRS Support Node (GGSN), which provide inter alia support for packetswitched services towards mobile stations, including mobilitymanagement, access control and control of packet data protocol contexts.In addition to this, the GGSN provides interworking with externalpacket-switched networks such as the public Internet.

1. A method in a radio communication system for channel type switching,said system comprising at least one control node which is connected to anumber of Radio Base Stations each covering certain geographical areasand providing communication services to user equipment in said areas andproviding connections to remote units in external networks, said methodcomprising the steps of: retrieving information regarding data packetsthat are sent on the uplink from said user equipment or on the downlinkfrom one of said remote units to one of said control nodes and checkingfor a correspondence to one of a selection of known packet header types;investigating recognized data packet headers in either direction fortraffic indications in order to make predictions of the expectabletraffic in consequence of said recognized data packet headers; andperforming a channel type switching to an appropriate channel typecomprising appropriate channel parameter settings on basis of saidinvestigated traffic indications.
 2. The method according to claim 1,wherein the channel type switching and parameter setting is performedfor an already existing communication connection or in parallel to theestablishment of a new communication connection on basis of trafficindications that have been received in the reverse direction.
 3. Themethod according to claim 1, further comprising an admission control fora downlink communication connection to be established by means ofchecking reported traffic restrictions and initiating possiblerestriction measures on basis of traffic indications that have beenreceived on the uplink.
 4. The method according to claim 3, wherein areceived uplink request is suppressed if the predicted additionaldownlink traffic exceeds a threshold value for the available downlinktransmission resources.
 5. The method according to claim 3, wherein areceived uplink request is delayed if the predicted additional downlinktraffic exceeds a threshold value for the available downlink resources.6. The method according to claim 3, wherein downlink bitrates arereduced for traffic that is not realtime sensitive.
 7. The methodaccording to claims 1, wherein a first group of investigated trafficindications refer to a protocol type and a traffic class.
 8. The methodaccording to claim 1, wherein a first group of investigated trafficindications refer to protocol contents.
 9. The method according to claim1, wherein a second group of investigated traffic indications refer tothe available radio network resources.
 10. The method according to claim1, wherein a third group of investigated traffic indications refer toproperties of the user equipment and the user subscription type.
 11. Amethod in a radio communication system for channel type switching, saidsystem comprising at least one control node which is connected to anumber of Radio Base Stations each covering certain geographical areasand providing communication services to user equipment in said areas andproviding connections to remote units in external networks, said methodcomprising the steps of: retrieving information regarding data packetsthat are sent to one of said control nodes and checking for acorrespondence to one of a selection of known packet header types;investigating recognized data packet headers for indications toterminate an existing downlink communication connection; and terminatingthe radio connection part of said existing communication connection. 12.An apparatus in a radio communication system for channel type switching,said system comprising at least one control node which is connected to anumber of Radio Base Stations each covering certain geographical areasand providing communication services to user equipment in said areas andproviding connections to remote units in external networks, saidarrangement comprising: means for retrieving information of data packetsthat are sent on the uplink from said user equipments or on the downlinkfrom one of said remote units to one of said control nodes and means forchecking for a correspondence to one of a selection of known packetheader types in a record; means for investigating recognized data packetheaders in either direction for traffic indications in order to makepredictions of the expectable traffic in consequence of said recognizeddata packet headers and means for performing a channel type switching toan appropriate channel type comprising appropriate channel parametersettings on basis of investigated traffic indications.
 13. The apparatusaccording to claim 12, further comprising means for checking reportedtraffic restrictions and initiating possible restriction measures for adownlink communication connection to be established on basis of thetraffic indications that have been received on the uplink.
 14. Thearrangement according to claim 12, wherein the control node consists ofa Radio Network Controller in a WCDMA-based radio communication system.15. An apparatus in a radio communication system for channel typeswitching, said system comprising at least one control node which isconnected to a number of Radio Base Stations each covering certaingeographical areas and providing communication services to userequipment in said areas and providing connections to remote units inexternal networks, said apparatus comprising: means for retrievinginformation of data packets to one of said control nodes and means forchecking for a correspondence to one of a selection of known packetheader types in a record; and means for investigating recognized datapacket headers, which comprise requests to terminate a communicationconnection, means for terminating the radio connection part of saidexisting communication connection.
 16. The apparatus according to claim15, wherein the control node consists of a Radio Network Controller in aWCDMA-based radio communication system.